摘要:
A process is provided to generate fluorescent molecules in the presence of target nucleic acids, but not in the absence of that target. Two probes, one bearing moiety A and the other bearing moiety B, bind to the target in a way that brings A and B together. A photon then converts A into A*, which can react with B to form a new species Z that is fluorescent. If A* does not encounter B, then A* reverts to form A. This allows the probe to have another opportunity to be activated should it be later bound near B. In one embodiment, a photoenolization creates A* as a diene; this reacts with a dienophile B in a Diels-Alder reaction. The linker Z may cause the linked probes to bind less tightly to the target, allowing the target to generate many fluorescent products, or be read through by a polymerase.
摘要:
This invention relates to nucleoside, nucleotide, and oligonucleotide analogs that incorporate non-standard nucleobase analogs, those that present a pattern of hydrogen bonds to a paired nucleobase analog in a complementary strand that is different from the pattern presented by adenine, guanine, cytosine, and thymine. Most specifically, this invention discloses and claims processes for amplifying nucleic acid analogs containing non-standard nucleobases using polymerase chain reactions, and combinations of non-standard nucleobases, analogs of standard nucleotides, and enzymes that perform this amplification. Most specifically, this invention is for the use of 2-thiothymidine triphosphate (2-thioTTP) instead of thymidine triphosphate in a six letter polymerase chain reaction that includes 2′-deoxyadenosine triphosphate, 2′-deoxyguanosine triphosphate, 2′-deoxycytidine triphosphate, 2′-deoxy-iso-guanosine triphosphate, and 2′-deoxy-iso-cytidine triphosphate, as well as their forms that contain side chain modifications. Because of the size and hydrogen bonding properties of the sulfur unit in 2-thioT, 2-thioT does not mispair effectively with the minor tautomer of isoG. This permits the PCR amplification of a six letter artificially expanded genetic information system, we examined the relative rates of misincorporation of 2-thioTTP and TTP opposite isoG using affinity electrophoresis with a fidelity-per-round of ca. 98%. The analogous PCR employing TTP has a fidelity-per-round of only ca. 93%. Therefore, this invention represents the first example of a six letter artificial genetic system that is amplifiable by a thermostable polymerase, and capable of Darwinian evolution.
摘要:
This invention provides compositions of matter that, when incorporated into an oligonucleotide, present to a complementary strand in a Watson-Crick pairing geometry a pattern of hydrogen bonds that is different from the pattern presented by adenine, guanine, cytosine, and thymine. Most specifically, this invention discloses and claims compositions of matter that present the same hydrogen bonding patterns as the isocytidine and isoguanosine nucleobases, but do not have unfavorable tautomeric forms, do not become disassociated from their sugar, and do not make major groove interactions, as much, as easily, or as strongly as isocytidine and isoguanosine.
摘要:
The disclosure describes building blocks for preparing oligonucleotides carrying non-standard nucleobases that can pair with complementary non-standard nucleobases so as to fit the Watson-Crick geometry, in that the resulting base pair joins a monocyclic six membered ring pairing with a fused bicyclic heterocyclic ring system composed of a five member ring fused with a six membered ring, with the orientation of the heterocycles with respect to each other and with respect to the backbone chain analogous to that found in DNA and RNA, but with a pattern of hydrogen bonds holding the base pair together different from that found in the AT and GC base pairs (a “non-standard base pair”).
摘要:
This invention concerns non-standard nucleotides that can form non-standard Watson-Crick nucleobase pairs having geometries similar to the geometries of standard nucleotide pairs, but that are joined by a non-standard hydrogen bonding schemes. Disclosed are processes that yield oligonucleotides that are semi-complementary to a standard oligonucleotide, where the region of semi-complementarity pairs one or more standard nucleotides with a non-standard nucleotide, or vice versa. Duplexes formed from two semi-complementary oligonucleotides are also inventions disclosed. The processes extending a primer annealed to an oligonucleotide template with a polymerase in the presence of a non-standard nucleoside triphosphate and a mixture of standard nucleoside triphosphates, where the non-standard triphosphate is incorporated opposite the standard triphosphate because it has available a protonated or deprotonated form, or a minor tautomeric form, that is complementary in the Watson-Crick sense to the standard nucleotide, even though in its normal form (neither protonated or deprotonated, or as its major tautomer) it is complementary in the Watson-Crick sense to a non-standard nucleobase. Also disclosed are processes that exploit an intermediary nucleoside, one whose nucleobase is partially complementary to both a standard nucleotide and a non-standard nucleotide at two of their three hydrogen bonding units. Also disclosed are intermediary nucleotides whose hydrogen bonding patterns are changed by chemical reagents. Also disclosed are the vice versa processes and process pairs where standard nucleotides are incorporated opposite non-standard nucleotides, yielding clonable products that can be sequenced to determine where non-standard nucleotides were present in the parent template oligonucleotide.
摘要:
This invention relates to the field of nucleic acid chemistry, more specifically to compositions of matter that are nucleic acid analogs, and processes that use them. Still more specifically, these compositions comprise two fragments of DNA-like molecules, each having one or more ends modified to carry a reactive group, where the reactive group on one fragment can form a transient covalent bond with the reactive group on the other under conditions of dynamic equilibrium to form a composite, where the composite can then bind to a target oligonucleotide, such as a DNA or RNA molecule. Most specifically, once the transient covalent bond forms, the composite serves as a primer for a template-directed polymerization using a DNA polymerase, an RNA polymerase, or a reverse transcriptase. Once incorporated, the epimerization causes the base pair to be destabilized, the duplex containing the epimerized nucleoside to likewise be destabilized, and the double strand to then disassociate. This leaves the template available to template the synthesis of another complementary oligonucleotide containing the epimerizing base.
摘要:
A method for making a model for the folded structure of a set of proteins from an evolutionary analysis of a set of aligned homologous protein sequences was claimed in Ser. No. 07/857,224. The instant application concerns methods for using these models. The first method is used to confirm or deny a hypothesis that two proteins are homologous, and is comprised of comparing a predicted structure model for one family of proteins with a predicted structure model for a second family of proteins, or an experimental structure for the second family, and deducing the presence or absence of homology based on the presence or absence of structural similarity flanking key residue motifs in the polypeptide sequence. The second method identifies mutations during the divergent evolution of a protein sequence that are potentially adaptive by identifying episodes during the divergent evolution of a family of proteins where there is a high absolute rate of amino acid substitution, or a high ratio of non-silent substitutions to non-silent substitutions. Amino acids that are changing during this episode are likely to be adaptive. The third is a method for identifying specific in vitro properties of the protein that are likely to play a physiological role in vivo in an organism. This methods involves synthesizing in the laboratory proteins having the reconstructed amino acid sequences of a protein before and after a period of rapid sequence evolution that characterizes adaptive substitution, measuring the in vitro properties of the protein before the episode of rapid sequence evolution, and then measuring the in vivo properties of the protein after the episode of rapid sequence evolution. The in vitro behaviors that remained unchanged through this episode are not likely to have adaptive significance physiologically. The in vitro behaviors that changed through this episode are likely to have adaptive significance physiologically. The fourth concerns method for organizing genome sized sequence databases.
摘要:
The disclosure describes building blocks for preparing oligonucleotides carrying non-standard nucleobases that can pair with complementary non-standard nucleobases so as to fit the Watson-Crick geometry, in that the resulting base pair joins a monocyclic six membered ring pairing with a fused bicyclic heterocyclic ring system composed of a five member ring fused with a six member ring, with the orientation of the heterocycles with respect to each other and with respect to the backbone chain analogous to that found in DNA and RNA, but with a pattern of hydrogen bonds holding the base pair together different from that found in the AT and GC base pairs (a "non-standard base pair").
摘要:
The disclosure describes new compositions of matter that are analogs of DNA and RNA containing heterocyclic bases that can form base pairs that fit the Watson-Crick geometry in that they involve a monocyclic six membered ring pairing with a fused bicyclic heterocyclic ring system composed of a five member ring fused with a six membered ring, with the orientation of the heterocycles with respect to each other and with respect to the backbone chain analogous to that found in DNA and RNA, but where these base pairs are joined by a pattern of hydrogen bonds different from that found in the AT and GC base pairs (a "non-standard base pair").
摘要:
This invention provides a method for preparing molecules that bind to a preselected receptor, whereby the receptor itself acts as an agent for either joining two ligand fragments to form a composite, tight binding ligand, or selects a composite ligand from a mixture in solution where ligand fragments are being joined and unjoined reversibly under equilibrium conditions.